The iPhone X's face-recognition system may be secure, but it could be super-annoying to use

Apple's new iPhone X will use face recognition to authenticate users instead of the Touch ID fingerprint sensor.Apple

With the just-unveiled iPhone X, Apple has introduced a new way for users to unlock their phones — they'll just look at their device.

The new $1,000 gadget has a built-in facial-recognition system that Apple says is more secure and will work just as well as the Touch ID fingerprint sensors in its other phones. How well it will work in practice is in anyone's guess, but I have my doubts.

Apple calls the new unlocking system Face ID. It's built around an advanced face-mapping camera system that authenticates you by scanning your face.

The new system replaces Touch ID. The front of the iPhone X is nearly completely covered by a glass screen, which meant there wasn't a way to put a physical home button in it. And Apple reportedly struggled to integrate a fingerprint sensor underneath the new screen.

The company knew that the move to a face-recognition system might cause people to worry that their phone could be unlocked with just a picture of their face or some kind of mask. But in introducing the system, Apple assured the public it had thought of those potential shortcomings and worked to address them.

According to Apple, Face ID won't be fooled by photographs or masks, and there is only one chance in a million that someone other than you would be able to unlock your phone with their face. At least nominally, that's much more secure than Touch ID, where there's a one-in-fifty-thousand chance that someone else could use their fingerprint to unlock your device.

Apple also worked hard on accuracy, to make sure that Face ID is instant and never misses a shot. The system maps over 30,000 points on users' faces, creating a unique model of each face that allows it to recognise individual users, even when their appearance changes. You can grow a beard, cut your hair, change your glasses, or wear a a hat or a scarf, and — at least according to Apple — Face ID will still be able to identify you.

The new phone's "TrueDepth" camera system is jam-packed with all the technology needed for Face ID to work.Apple

All the information about your face is safely stored inside your iPhone. Apple has no way to access it. Nor can anyone else, at least not remotely.

Apple likely knew that in replacing Touch ID, a technology that iPhone owners use frequently, it had to get the replacement right. I haven't tried Face ID myself yet, but the first reports coming out of the Steve Jobs Theater's hands-on area seem to indicate that it's well developed.

Once the phone is in circulation and security researchers have gotten their hands on it, we'll see how well Apple has really addressed the potential privacy and security issues inherent in a face-recognition system.

But even if it did actually solve those, Face ID is likely to present another big practical problem, especially when compared with fingerprint sensors. And it all has to do with convenience.

People unlock their phones literally hundreds of time every day. Many have become accustomed to the iPhone's simple one-touch, multi-purpose gesture. You click the home button, and in one go, you are both securely authenticated and logged in. It's something so simple.

In fact, there's a good chance that when you're getting ready to use your phone, you're already placing your thumb on the home button before you pull it out of your pocket, so that the device is already unlocked by the time it's in front of your eyes.

That's something you're just not going to be able to do with Face ID. And no matter how precise and quick it is, it's inevitably going to take more time to unlock your phone than a fingerprint sensor.

With Touch ID, unlocking your phone is essentially a one-step process. As you click on the home button, the phone scans your fingerprint and unlocks.

By contrast, with Face ID, unlocking your iPhone X will become a three-step affair. It would go like this: You lift your iPhone X to wake it up, place it in front of your eyes so that Face ID can recognise you, and, once it does, you then swipe up to get to the home screen.

Face ID will also make it impossible to unlock your phone in some of the same ways that a fingerprint sensor can. Right now, for example, if your phone is lying on a table in front of you, you can easily unlock it with your index finger without having to pick it up or look at it directly. But with the iPhone X, you would have to grab the phone, place it in front of you, and then swipe up to get to the home screen.

The new face-recognition system also seems like it's going to be very awkward when making mobile payments. Apple Pay and Android Pay have essentially replaced my wallet. I rely on my phone to pay for things all the time. In London, I use my phone to pay for both the Underground and bus services. I also use it to pay for goods in virtually every shop in the city.

To make a mobile payment with my current phone, Google's Pixel XL, I just place my index finger on its fingerprint scanner, which is located on its back. It unlocks the phone, and I can pay for stuff. Apple Pay works in a similar fashion.

Face ID will be more difficult to use. You'll have to line up the phone in front of your face, have it recognise you, then move the phone close to the terminal. It's not exactly "tap to pay," which is what Apple promised with Apple Pay and Touch ID. And the extra time needed to use Face ID to make a payment could prove stressful when you are queuing and other people are waiting for their turn.

It may work better in practice then I'm describing here. But even an extra two or three seconds could make for a rather unpleasant experience, especially when you multiply it by the many times a day users need to unlock their phones or make payments with them.

I look forward to actually testing an iPhone X — which otherwise looks like it will be a stellar phone — and will wait until then to make a final judgment on Face ID. Here's hoping I won't have to go back to using a plain old PIN.